I really don’t think the biggest miracle of Purim was being saved from Haman. I think the biggest miracle came before that. Imagine if we faced the same threat as the Jews of Achashveirosh’s kingdom. What would the reaction be?
First you would have those in denial: don’t take it so seriously, it’s only words, nothing will come of it.
Then you would have the Michael Lerner/George Soros types who would say it’s our own fault. For those living in the various parts of the kingdom, why are you not more assimilated? Mordechai, why not just leave Haman alone (good question -- see Maharal)? For those living in Eretz Yisrael, who do you insist on building a Mikdash, or practicing apartheid-like tactics against the natives?
The latter point would be echoed by voices from the opposite end of the spectrum: all the problems are the fault of the “Tziyonim” who already started building a Mikdash before getting official word that the 70 years of galus are over.
Then you would have the reaction to Esther’s call for a fast – on Pesach no less! You would have those who would inevitably raise accusations of her fomenting some kind of feminist uprising vs. those who would allow debate as to whether she should be called “Malakanit,” “Malkah,” some other title to eclipse the significance of the message.
I could go one, but you get the point. Am I too cynical? Maybe. But I really think the nes of Purim was the acceptance that there was an inescapable existential danger to the tzibur, that tshuvah and ta’anis were essential and necessary responses, and that there was no other recourse. For all the grumblings the gemara tells us about as to whether Mordechai had a role in antagonizing Haman or not, bottom line is when the chips were down and action was needed, the tzibur put their trust in Mordechai and Esther's advice and responded. “Zman kehila la’kol hi.”